- REACTION PATHS AND NEW MECHANISTIC ASPECTS OF THE PROTON-CATALYZED REACTION OF 3-ALKYLINDOLES WITH ARYLALDEHYDES
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The mechanism of the proton-catalyzed reaction of 3-alkylindoles with arylaldehydes is elucidated by the isolation of stable intermediates and products, and by the selective control of their transformations in the course of reaction.The aldehyde electrophile attacks at N1, C2 and C3 on the indole enamine structure with the temperature, the reaction time and the proton concentration controlling the relative quantities and distribution of products.It was established indirectly that an ipso-attack by intermediary cations with iminium and indolenine structure takes placeat the 3- position of 3-alkylated indoles.This was made possible by the isolation of hitherto unknown tetrahydropyrrolodiindoles 14, 17.These compounds should be formed from intermediary indolylmethyl-indoleninium ions 13, 11, which are trapped by stereoelectronic controlled intramolecular cyclization.
- Dittmann, Klaus,Pindur, Ulf
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p. 1079 - 1093
(2007/10/02)
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